Longtubes not worth it with a supercharger?
01-09-2007, 05:10 AM
#1
Longtubes not worth it with a supercharger? I was doing some research on a header for my D1SC combo (14/15psi, with a hit of nitrous on top of it) and i came across this post. It deals exclusively with supercharged applications so I'm posting it in here.
Anyone else agree or disagree with this? I find this VERY interesting. Are we peeing in the wind with longtubes on blown applications??? 
Originally Posted by 300bhp/ton
Also you are totally wrong with scavenging. On a supercharged setup the intake air is being forced into the combustion chamber at above atomospheric pressure. Therefore the 5th cycle in the combustion process (induced via scavenging) is eliminated.
Originally Posted by 300bhp/ton
Lastly, as explained in my above post scavenging doesn't take place with a supercharger and as the primary purpose of a LT header is to scavenge you probably won't see any benefit over other alternatives.
Flow rate is going to be largly dictated by primary diameter, the lenght will not be a real concern. So for this reason a set of shorties or mids would probably work just as well as LT's. This may be a cheaper option as people are always selling shorties because on a n/a motor they don't do anytihng (essentially they don't scavenge) but with FI it's a different ball game.
So in theory a good set of shorties should see similar/same gains as LT's on a supercharged car.
On a 03/4 Cobra shorties are generally worth ~25rwhp and LT's gain the same. The LS1 is no different in this respect.
But at the end of the day it's your money, so please go and research this rather than just taking my word on it.
Flow rate is going to be largly dictated by primary diameter, the lenght will not be a real concern. So for this reason a set of shorties or mids would probably work just as well as LT's. This may be a cheaper option as people are always selling shorties because on a n/a motor they don't do anytihng (essentially they don't scavenge) but with FI it's a different ball game.
So in theory a good set of shorties should see similar/same gains as LT's on a supercharged car.
On a 03/4 Cobra shorties are generally worth ~25rwhp and LT's gain the same. The LS1 is no different in this respect.
But at the end of the day it's your money, so please go and research this rather than just taking my word on it.
01-09-2007, 06:55 AM
#4
While scavenging may not be a big issue cylinder dilution from added backpressure sure is.
I picked up nearly 50rwhp switching from JBA shorties to FLP LTs back in 2000 on a P1SC car. If someone made a decent short header for these with a large collector and 1.75 primaries that may hold somewhat true. Decent headers are cheap these days, unless you are from kalifornia there is no reason not to put them on.
I picked up nearly 50rwhp switching from JBA shorties to FLP LTs back in 2000 on a P1SC car. If someone made a decent short header for these with a large collector and 1.75 primaries that may hold somewhat true. Decent headers are cheap these days, unless you are from kalifornia there is no reason not to put them on.
01-09-2007, 08:31 AM
#5
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I would strongly disagree that scavenging is eliminated.
regardless of the theory behind it, LT's DO help supercharged motors, period. thousands of dyno runs and time slips have proven it.
regardless of the theory behind it, LT's DO help supercharged motors, period. thousands of dyno runs and time slips have proven it.
01-09-2007, 11:38 AM
#6
Originally Posted by BIG BAD BLACKSS
I was doing some research on a header for my D1SC combo (14/15psi, with a hit of nitrous on top of it) and i came across this post. It deals exclusively with supercharged applications so I'm posting it in here.
Anyone else agree or disagree with this? I find this VERY interesting. Are we peeing in the wind with longtubes on blown applications???
Anyone else agree or disagree with this? I find this VERY interesting. Are we peeing in the wind with longtubes on blown applications???
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01-09-2007, 01:59 PM
#9
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The majority of your benifits will come at lower / mid-range rpm where there isn't any significant boost. With the vast majority of people refusing to run cams that promote chamber scavenging a strong signal from the headers will help a great deal. Shortys will also scavenge, but at an rpm that will disassemble the valve train.
Long tubes are always effective off idle - up and can really change the character of the car. As with everything else, the rest of the combination will help determine how effective they are.
In a max boost only high rpm situation large tube shortys with little exhaust tubing afterwards will probably not give up much in peak numbers, but the area under the curve will be fatter with the LT's. Think alchohol or fuel dragster, and then funny car with the longer zoomies required by the drop body. A funny car engine isn't as peaky and has a bit wider powerband due strictly to the different exhaust requirements.
Apples, oranges...I know.
Long tubes are always effective off idle - up and can really change the character of the car. As with everything else, the rest of the combination will help determine how effective they are.
In a max boost only high rpm situation large tube shortys with little exhaust tubing afterwards will probably not give up much in peak numbers, but the area under the curve will be fatter with the LT's. Think alchohol or fuel dragster, and then funny car with the longer zoomies required by the drop body. A funny car engine isn't as peaky and has a bit wider powerband due strictly to the different exhaust requirements.
Apples, oranges...I know.
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01-09-2007, 03:51 PM
#11
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I just look at what the blower race guys do in NMRA Renegade and Drag Radial.... Long tubes with the biggest collectors possible... 3.5" a lot of the time, I'm betting 4" maybe.
01-09-2007, 04:52 PM
#13
Originally Posted by MeentSS02
You can believe what you want, but I'd take 300bhp/ton's advice with a grain of salt. He quotes a lot of texts and theory, but has no real world experience with any of it. I stopped listening to him long ago...theory can only get you so far in this world.
could not have said it better myself.. all he does is theorize "what if" and "probability".. which is fine.. but he makes it sound factual when nothing was/is done to prove it.
